The traditional referral guidelines for lung transplant in CF are largely based on a FEV <30% predicted. The optimal timing for referral has not been determined. Other factors may be important in predicting the risk of death in these patients. The presence of emerging infectious CF pathogens may be associated with a higher risk of death. These factors have not been tested in other studies. The identification of the above variables as risk factors for death may be used to modify the referral process or pre-transplantation therapy and improve survival of CF patients awaiting transplantation. We propose to perform a three-center retrospective cohort study, with the following aims: (1) determine the association of emerging CF pathogens (including Aspergillus spp. And MRSA) pretransplant with mortality while awaiting lung transplantation: before and after referral for lung transplantation, (2) determine the association of poor nutritional status (including shorter height) pretransplant with mortality while awaiting lung transplantation (3) determine the association of poor pulmonary function (including % predicted FEV1) pretransplant with mortality while awaiting lung transplantation.